Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China

Yan Bi, Weiwei Yu, Wenbiao Hu, Hualiang Lin, Yuming Guo, Xiao Nong Zhou, Shilu Tong

Research output: Contribution to journalArticleResearchpeer-review

27 Citations (Scopus)

Abstract

Background: Malaria remains a public health problem in the remote and poor area of Yunnan Province, China. Yunnan faces an increasing risk of imported malaria infections from Mekong river neighboring countries. This study aimed to identify the high risk area of malaria transmission in Yunnan Province, and to estimate the effects of climatic variability on the transmission of Plasmodium vivax and Plasmodium falciparum in the identified area. Methods. We identified spatial clusters of malaria cases using spatial cluster analysis at a county level in Yunnan Province, 2005-2010, and estimated the weekly effects of climatic factors on P. vivax and P. falciparum based on a dataset of daily malaria cases and climatic variables. A distributed lag nonlinear model was used to estimate the impact of temperature, relative humidity and rainfall up to 10-week lags on both types of malaria parasite after adjusting for seasonal and long-term effects. Results: The primary cluster area was identified along the China-Myanmar border in western Yunnan. A 1°C increase in minimum temperature was associated with a lag 4 to 9 weeks relative risk (RR), with the highest effect at lag 7 weeks for P. vivax (RR = 1.03; 95% CI, 1.01, 1.05) and 6 weeks for P. falciparum (RR = 1.07; 95% CI, 1.04, 1.11); a 10-mm increment in rainfall was associated with RRs of lags 2-4 weeks and 9-10 weeks, with the highest effect at 3 weeks for both P. vivax (RR = 1.03; 95% CI, 1.01, 1.04) and P. falciparum (RR = 1.04; 95% CI, 1.01, 1.06); and the RRs with a 10% rise in relative humidity were significant from lag 3 to 8 weeks with the highest RR of 1.24 (95% CI, 1.10, 1.41) for P. vivax at 5-week lag. Conclusions: Our findings suggest that the China-Myanmar border is a high risk area for malaria transmission. Climatic factors appeared to be among major determinants of malaria transmission in this area. The estimated lag effects for the association between temperature and malaria are consistent with the life cycles of both mosquito vector and malaria parasite. These findings will be useful for malaria surveillance-response systems in the Mekong river region.

Original languageEnglish
Article number357
Number of pages12
JournalParasites and Vectors
Volume6
Issue number1
DOIs
Publication statusPublished - 17 Dec 2013
Externally publishedYes

Keywords

  • China-myanmar border area
  • Climatic variables
  • Distributed lag nonlinear model
  • Plasmodium falciparum
  • Plasmodium vivax
  • Spatial cluster area

Cite this

Bi, Yan ; Yu, Weiwei ; Hu, Wenbiao ; Lin, Hualiang ; Guo, Yuming ; Zhou, Xiao Nong ; Tong, Shilu. / Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China. In: Parasites and Vectors. 2013 ; Vol. 6, No. 1.
@article{c46a5b8b7ff347ef8526d05208cae15e,
title = "Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China",
abstract = "Background: Malaria remains a public health problem in the remote and poor area of Yunnan Province, China. Yunnan faces an increasing risk of imported malaria infections from Mekong river neighboring countries. This study aimed to identify the high risk area of malaria transmission in Yunnan Province, and to estimate the effects of climatic variability on the transmission of Plasmodium vivax and Plasmodium falciparum in the identified area. Methods. We identified spatial clusters of malaria cases using spatial cluster analysis at a county level in Yunnan Province, 2005-2010, and estimated the weekly effects of climatic factors on P. vivax and P. falciparum based on a dataset of daily malaria cases and climatic variables. A distributed lag nonlinear model was used to estimate the impact of temperature, relative humidity and rainfall up to 10-week lags on both types of malaria parasite after adjusting for seasonal and long-term effects. Results: The primary cluster area was identified along the China-Myanmar border in western Yunnan. A 1°C increase in minimum temperature was associated with a lag 4 to 9 weeks relative risk (RR), with the highest effect at lag 7 weeks for P. vivax (RR = 1.03; 95{\%} CI, 1.01, 1.05) and 6 weeks for P. falciparum (RR = 1.07; 95{\%} CI, 1.04, 1.11); a 10-mm increment in rainfall was associated with RRs of lags 2-4 weeks and 9-10 weeks, with the highest effect at 3 weeks for both P. vivax (RR = 1.03; 95{\%} CI, 1.01, 1.04) and P. falciparum (RR = 1.04; 95{\%} CI, 1.01, 1.06); and the RRs with a 10{\%} rise in relative humidity were significant from lag 3 to 8 weeks with the highest RR of 1.24 (95{\%} CI, 1.10, 1.41) for P. vivax at 5-week lag. Conclusions: Our findings suggest that the China-Myanmar border is a high risk area for malaria transmission. Climatic factors appeared to be among major determinants of malaria transmission in this area. The estimated lag effects for the association between temperature and malaria are consistent with the life cycles of both mosquito vector and malaria parasite. These findings will be useful for malaria surveillance-response systems in the Mekong river region.",
keywords = "China-myanmar border area, Climatic variables, Distributed lag nonlinear model, Plasmodium falciparum, Plasmodium vivax, Spatial cluster area",
author = "Yan Bi and Weiwei Yu and Wenbiao Hu and Hualiang Lin and Yuming Guo and Zhou, {Xiao Nong} and Shilu Tong",
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Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China. / Bi, Yan; Yu, Weiwei; Hu, Wenbiao; Lin, Hualiang; Guo, Yuming; Zhou, Xiao Nong; Tong, Shilu.

In: Parasites and Vectors, Vol. 6, No. 1, 357, 17.12.2013.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China

AU - Bi, Yan

AU - Yu, Weiwei

AU - Hu, Wenbiao

AU - Lin, Hualiang

AU - Guo, Yuming

AU - Zhou, Xiao Nong

AU - Tong, Shilu

PY - 2013/12/17

Y1 - 2013/12/17

N2 - Background: Malaria remains a public health problem in the remote and poor area of Yunnan Province, China. Yunnan faces an increasing risk of imported malaria infections from Mekong river neighboring countries. This study aimed to identify the high risk area of malaria transmission in Yunnan Province, and to estimate the effects of climatic variability on the transmission of Plasmodium vivax and Plasmodium falciparum in the identified area. Methods. We identified spatial clusters of malaria cases using spatial cluster analysis at a county level in Yunnan Province, 2005-2010, and estimated the weekly effects of climatic factors on P. vivax and P. falciparum based on a dataset of daily malaria cases and climatic variables. A distributed lag nonlinear model was used to estimate the impact of temperature, relative humidity and rainfall up to 10-week lags on both types of malaria parasite after adjusting for seasonal and long-term effects. Results: The primary cluster area was identified along the China-Myanmar border in western Yunnan. A 1°C increase in minimum temperature was associated with a lag 4 to 9 weeks relative risk (RR), with the highest effect at lag 7 weeks for P. vivax (RR = 1.03; 95% CI, 1.01, 1.05) and 6 weeks for P. falciparum (RR = 1.07; 95% CI, 1.04, 1.11); a 10-mm increment in rainfall was associated with RRs of lags 2-4 weeks and 9-10 weeks, with the highest effect at 3 weeks for both P. vivax (RR = 1.03; 95% CI, 1.01, 1.04) and P. falciparum (RR = 1.04; 95% CI, 1.01, 1.06); and the RRs with a 10% rise in relative humidity were significant from lag 3 to 8 weeks with the highest RR of 1.24 (95% CI, 1.10, 1.41) for P. vivax at 5-week lag. Conclusions: Our findings suggest that the China-Myanmar border is a high risk area for malaria transmission. Climatic factors appeared to be among major determinants of malaria transmission in this area. The estimated lag effects for the association between temperature and malaria are consistent with the life cycles of both mosquito vector and malaria parasite. These findings will be useful for malaria surveillance-response systems in the Mekong river region.

AB - Background: Malaria remains a public health problem in the remote and poor area of Yunnan Province, China. Yunnan faces an increasing risk of imported malaria infections from Mekong river neighboring countries. This study aimed to identify the high risk area of malaria transmission in Yunnan Province, and to estimate the effects of climatic variability on the transmission of Plasmodium vivax and Plasmodium falciparum in the identified area. Methods. We identified spatial clusters of malaria cases using spatial cluster analysis at a county level in Yunnan Province, 2005-2010, and estimated the weekly effects of climatic factors on P. vivax and P. falciparum based on a dataset of daily malaria cases and climatic variables. A distributed lag nonlinear model was used to estimate the impact of temperature, relative humidity and rainfall up to 10-week lags on both types of malaria parasite after adjusting for seasonal and long-term effects. Results: The primary cluster area was identified along the China-Myanmar border in western Yunnan. A 1°C increase in minimum temperature was associated with a lag 4 to 9 weeks relative risk (RR), with the highest effect at lag 7 weeks for P. vivax (RR = 1.03; 95% CI, 1.01, 1.05) and 6 weeks for P. falciparum (RR = 1.07; 95% CI, 1.04, 1.11); a 10-mm increment in rainfall was associated with RRs of lags 2-4 weeks and 9-10 weeks, with the highest effect at 3 weeks for both P. vivax (RR = 1.03; 95% CI, 1.01, 1.04) and P. falciparum (RR = 1.04; 95% CI, 1.01, 1.06); and the RRs with a 10% rise in relative humidity were significant from lag 3 to 8 weeks with the highest RR of 1.24 (95% CI, 1.10, 1.41) for P. vivax at 5-week lag. Conclusions: Our findings suggest that the China-Myanmar border is a high risk area for malaria transmission. Climatic factors appeared to be among major determinants of malaria transmission in this area. The estimated lag effects for the association between temperature and malaria are consistent with the life cycles of both mosquito vector and malaria parasite. These findings will be useful for malaria surveillance-response systems in the Mekong river region.

KW - China-myanmar border area

KW - Climatic variables

KW - Distributed lag nonlinear model

KW - Plasmodium falciparum

KW - Plasmodium vivax

KW - Spatial cluster area

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U2 - 10.1186/1756-3305-6-357

DO - 10.1186/1756-3305-6-357

M3 - Article

VL - 6

JO - Parasites and Vectors

JF - Parasites and Vectors

SN - 1756-3305

IS - 1

M1 - 357

ER -